Suture with wound healing filament

ABSTRACT

A suture and ligature material useful in accelerating the healing of wounds comprising twisted or braided filaments (a) of pure aluminum and stainless steel or (b) of pure magnesium and stainless steel filaments.

United States Patent O SUTURE WITH WOUND HEALING FILAMENT Winfred Hirsch, Plainview, N.Y., assignor to Edward Week & Company, Inc., Long Island City, N.Y. No Drawing. Continuation-impart of application Ser. No.

531,768, Mar. 4, 1966. This application June 19, 1968,

Ser. No. 738,098

Int. Cl. A611 17/00 US. Cl. 128-335.5 14 Claims ABSTRACT OF THE DISCLOSURE A suture and ligature material useful in accelerating the healing of wounds comprising twisted or braided filaments (a) of pure aluminum and stainless steel or (b) of pure magnesium and stainless steel filaments.

CROSS REFERENCES This is a continuation-in-part of application Ser. No. 531,768 filed Mar. 4, 1966, for Sutures and Ligatures Adapted for the Acceleration of Wound Healing, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates to sutures and ligatures and more particularly to sutures and ligatures useful in accelerating the healing of wounds.

-It has been discovered that sutures, when made of a single filament of pure aluminum or magnesium, actually accelerate the healing of the Wound in which they are used, apparently by means of an electrochemical interaction with the body tissues surrounding the wound. Monofilament sutures made of aluminum, however, are not satisfactory because they are brittle and do not have the knot-pull tensile strength characteristics required by the United States Pharmacopeia (USP) specifications for such sutures. Knot-pull strength is the pulling force required to break a surgically knotted suture. Using this definition, according to USP requirements, a size 30 monofilament Class III (metallic) suture should have a knot-pull tensile strength of not less than 1.36 kg. or about 3 lbs. A typical monofilament pure aluminum suture of this size, however, does not meet this requirement. In addition, such sutures have a high rate of dissolution in the tissues, thus lessening their strength and ability to hold wounds closed. Also though aluminum and magnesium serve to accelerate healing of the wound, it is desirable to have wounds heal even faster than is possible using either of these materials by itself.

SUMMARY OF THE INVENTION I have discovered that all of these disadvantages can be overcome by forming a suture either of stainless steel and pure aluminum filaments or of stainless steel and pure magnesium. In either case the filaments are preferably braided or twisted together. The stainless steel gives the suture the initial strength it needs to meet USP requirements and since it does not dissolve or become resorbed by the tissues, it maintains the strength of the suture as long as it is in the wound. :In addition, a unique advantage of such suture material is that it accelerates wound healing faster than any other known suture or ligature material. Thus, though it is known that pure aluminum or magnesium will accelerate wound healing, I have discovered that the rate of wound healing can be accelerated even more if filaments of one or the other of these pure metals 3,572,343 Patented Mar. 23, 1971 is twisted or braided with stainless steel. The additional acceleration in wound healing caused by this new suture material appears to be due to a synergetic electromotive activity between the metals.

In a suture according to the invention, the aluminum or magnesium should approach as closely as possibly 100% purity because the wound-healing ability of these metals diminishes with the number and amount of alloying materials and contaminants they contain. Aluminum filaments comprising in excess of 99% pure aluminum, 0.76% magnesium and no more than 0.000X% traces each of silicon, iron, copper, silver and manganese have been shown to be satisfactory. Magnesium filaments containing no more than 5% impurities or alloying metals are also usable, though higher purities are desirable. The stainless steel should be of surgical quality. In particular, Babcock 18-8, type 316- and type 316L, are especially useful in a suture according to this invention. Before the filaments are twisted or braided together to form the suture, they should be annealed to a dead-soft condition to reduce brittleness and susceptibility to work hardening.

The invention also includes the step of stretching the stainless steel filaments elastically about 10% more than the aluminum or magnesium as the suture is being braided or twisted. This way when the suture is put into use, the stainless steel will absorb virtually all the load, and the aluminum is left relatively tension-free except for those tension and compression stresses caused by tying the suture into a surgical knot.

BRIEF DESCRIPTION OF THE INVENTION Sutures according to this invention may have as few as two or as many as 48 or more filaments including between 1-24 or more aluminum or magnesiiun wound-healing filaments and l-24 or more stainless steel supporting filaments. The former should comprise between about 20% and and preferably about 50% of the exposed peripheral surface area of the suture. By exposed peripheral surface area is meant that portion of the suture which is capable of coming into direct contact with the tissues being sewn together. Thus, in a twisted suture having concentrically laid filaments, the core, which has no exposed surface area at all, should comprise stainless steel.

The particular manner in which the two types of filaments are twisted together is not material as long as the total exposed surface area is within the prescribed range. Thus, they can be braided, twisted into either a concentric or a bunch configuration, or given a rope lay in which the filaments are first twisted in one direction into strands and then the strands themselves twisted, preferably in the opposite direction to form the suture. Regardless of the way in which they are twisted, all the filaments need not be of the same diameter. For example, providing the surface area limitations are met, the woundhealing filaments can be of smaller or larger diameter than the supporting filaments. In addition, the number of turns per inch each filament makes preferably ranges from 5 to 18, depending upon the total number of filaments in the suture and the diameter of each. The optimum number of turns is determined primarily by the size of the suture and the number and diameter of its filaments. The standard USP nonabsorbable suture sizes are listed in Table 1 below and for each of the more common sizes Table 2 shows the optimum turns per inch for twisted aluminum-stainless steel sutures. Suture construction is indicated first by the number and type of filaments, second by the optimum turns per inch and third by the diameter of each of the filaments in inches.

TABLE 1 Diameter (mm.) Diameter (inches) USP Sizes Minimum Maximum Minimum Maximum TABLE 2 Number and type oi oi filaments Filaments- Optimum, Diameter in USP sizes Al S.S turns/inch inches 2 1 3x0.001 3 3 6 0 X 0.001 2 2 7 4 x 0.0015 3 3 6-7 6 X 0. 0015 6-0 2 2 6-7 4 X 0. 002

2 2 67 4 x 3 4 7 x H 4 3 7x0 00197 H 4 4 7-8 8 x 0 00315 4 4 7-8 8 x 0.002 4 4 7-8 8 a 0. 003 4 3 8 7 x 0 00315 3 4 8 7 X 0 00315 30 12 12 7 24 x 0. 0014 0 10 7 19 x 0. 0015 10 9 7 10 x 0. 00107 0 0 8 18 x 0. 00?. 4 4 0 8 X 0.004 3 4 8 7 x 0.0045 4 3 8 7 x 0. 00472 0 3 4 8 7 x 0. 00472 24 24 481:0.0016 9 10 9 10 x 0. 00315 4 4 7 8 x 0.005 1 5 7 X 0. 005 24 24 7 48 X 0.002

Preferably in sutures with up to and including seven filaments, the filaments are twisted directly into a concentric crosss-ectional configuration. Sutures with more than seven filaments may also be twisted in a rope lay in which some of the filaments are given a left-hand twist to form strands which are then given a right-hand twist to form the suture. A concentric configuration is possible with as many as 49 or more filaments. After the suture is formed, its ends are cut. A surgical adhesive may be added to prevent the filaments from unraveling, though in the case of a braided suture, they can be left without adhesive. In addition, if desired, one of the ends can be connected to a needle in a known manner.

Example A satisfactory size 3-0 twisted suture according to the invention can be made from four dead-soft pure aluminum filaments and four Babcock 18-8 dead-soft stainless steel filaments, all of 0.003 inch diameter. The filaments can be twisted concentrically by hand or on a conventional planetary stranding machine. In either case, conventional friction clamps can be used to apply the necessary tension to the stainless steel filaments during twisting. About 10% more tension should be applied to the stainless steel than to the aluminum and in no event should the aluminum filaments be stretched beyond their elastic limit. Another way to apply the tension is to attach a suitable weight to one end of each of the stainless steel filaments to keep the tension even during twisting regardless of whether the suture is braided slowly or quickly. The center filament forming the core of the suture is stainless steel so that the sutures outer surface has four aluminum and hree sta nl ss. steel filaments. Once the suture is formed, it is preferably annealed to bring both metals back to a dead-soft condition.

Though in the example given the stainless steel filaments were put under about 10% more tension during twisting than the aluminum, this aspect of the process of forming a suture according to the invention is not essential. It can be completely omitted if desired. Only the presence of the aluminum and stainless steel filaments is necessary to achieve the synergistic action essential to achieving the increased wound-healing rate.

If the extra wound-healing action of an aluminum: stainless steel or magnesium-stainless steel combination is not desired or needed, a perfectly satisfactory woundhealing suture or ligature can be formed from combining aluminum or magnesium filaments with various other supporting materials which are also suitable for use as sutures. Thus, Dacron, nylon, Marlex, cotton, silk, polyester fiber or certain other conventional suture materials can be used as supporting fibers. When Dacron, nylon, Marlex or polyester fiber are used, however, it is esential that they be dimensionally stabilized before twisting or braiding with the wound-healing material. Otherwise, these supporting materials would stretch too much under tension and let the aluminum or magnesium carry so much of the load on the suture that it would be likely to break.

Stabilizing these materials is accomplished by a known heat treatment process in a dry atmosphere in which the material, such as Dacron is brought up to a temperature at least 10 F. higher than that to which it is expected the suture will be later exposed. By thermally setting the material in this manner, the elasticity is taken out of it, and when twisted or braided with either aluminum or magnesium, it will absorb more of the load to which the suture is subjected. The twisting or braiding of these filaments as with those of stainless steel is done conventionally and if desired as a safety precaution, to insure that too much stress is not placed on the wound-healing filaments, the supporting filaments can be placed under a higher tension during the twisting or braiding than the magnesium or aluminum. The amount of tension which should be used depends on the degree to which the elasticity has been taken out of the material, but it is usually desirable to use as much tension as at least onehalf the knot-pull breaking strength of the USP standard for the suture being made. This way, only a minor portion of the tensile stress on the suture will be absorbed by the aluminum or magnesium to these materials will be less likely to break.

It will be understood that various changes in the details, materials, steps and arrangements of parts, which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the claims.

What is claimed is:

1. A multiple filament suture useful in closing wounds and in accelerating the healing thereof, said suture comprising:

at least one non-reactive filament made of non-absorbable surgical suture material; and

at least one filament made of absorbable non-toxic metal which is reactive with wound tissues to accelerate healing thereof, said second filament being selected from the group consisting of substantially pure aluminum and substantially pure magnesium; said first and second filaments being coextensive and extending throughout the length of said suture.

2. The combination according to claim -1 wherein the reactive filament comprises pure aluminum and the nonreactive filament comprises surgical stainless steel.

3. The combination according to claim 1 wherein the reactive filament comprises pure magnesium and the nonreactive filament comprises surgical stainless steel.

4. The suture of claim 1 wherein the filaments are twisted together, said non-reactive filaments being under at least 10% more tension than said reactive metal filaments.

5. The suture of claim '1 wherein the filaments are braided together to form the suture.

6. The suture of claim 1 wherein said reactive metal filaments comprise a plurality of dead-soft pure aluminum filaments, said reactive metal filaments being twisted together with said non-reactive filaments which comprise not more than the same number of dead-soft surgical stainless steel filaments, said stainless steel filaments being subjected during formation of said suture to a tension about 10% greater than that to which said aluminum filaments are subjected, the suture being annealed after formation to return the filaments to a dead-soft condition.

7. The suture of claim 1 wherein said non-reactive filament is made of a non-toxic metal adapted to be synergetic with said reactive filament to further enhance the healing effect of said suture.

8. The combination according to claim 7 wherein there are a plurality of reactive and non-reactive filaments in the suture and the reactive filaments comprise between about 20% and 80% of the surface area of the suture which is capable of coming into direct contact with the wound.

9. The combination according to claim 8 wherein the reactive filaments comprise about 50% of the surface area of the suture which is capable of coming into direct contact with the wound.

10. The combination according to claim 9 wherein the reactive filaments comprise pure aluminum and the non- 3 reactive filaments comprise surgical stainless steel.

11. The suture of claim 10 wherein the filaments are twisted together, said surgical stainless steel filaments being under at least 10% more tension than said aluminum filaments.

12. The suture of claim 1 wherein said non-reactive filament is a non-metal surgical suture.

13..The combination according to claim 12 wherein the nonmetal suture filament comprises a selected member of the group consisting of Dacron, nylon, Marlex and polyester fiber.

14. The suture of claim 12 wherein the metal filaments are twisted with the non-metal filaments in such a manner that the metal filaments comprise about 50% of the surface area of the suture which is capable of coming into direct contact with the wound, the non-metal filaments being subject during twisting to a tension about equal to the knot-pull tensile strength according to USP standards of the suture.

15 References Cited ,UNITED STATES PATENTS 1,468,323 9/1923 Olson 57-144X 2,094,578 10/ 1937 Blumenthal et al. 129-3355 3,477,436 11/1969 Sawyer 128335.5 2,591,063 4/1952 Goldberg 128335.5

FOREIGN PATENTS 231,037 3/1925 Great Britain 128335.5

OTHER REFERENCES Johnson & Johnson Handbook for Sutures, 3rd edition, 1931, pp. 8-9 relied on.

Wue et al., Surgery, vol. 61, No. 2, pp. 242-247, 0 February 1967.

DALTON L. TRULUCK, Primary Examiner :U.S. Cl. X.R. 

